The present invention relates to a novel Ashbya gossypii promoter and its use for gene expression.
Filamentous fungi are important organisms for biotechnology owing to their characteristic of producing interesting constituents. These constituents which are formed by fungi include not only low-molecular-weight compounds such as organic acids, antibiotics or vitamins, but also higher-molecular-weight compounds such as enzymes, nonenzyme proteins or other biopolymers.
It is a general aim of biotechnology to optimize the production of such constituents by the fungi. Methods which are used to this end are, inter alia, also recombinant methods. These methods involve, for example, overexpressing individual genes or groups of genes in the filamentous fungus in question. These genes can be derived from the organism in which they are expressed, but also from other organisms.
In all cases, it is necessary to be able to govern the expression of the genes to be expressed. All the genes which are expressed in all organisms have a promoter region 5xe2x80x2 of the encoding sequence. This region is responsible for the start of the transcription itself, and also for transcriptional regulation. As a rule, this regulation is done by binding transcription factors to regulatory sequences within the promoter region. As a rule, promoters are freely portable, i.e. a promoter of one gene may be used for governing the transcription of another gene. This governing of the new gene is then, as a rule, identical with the governing of the original gene from which the promoter is derived. Thus, known promoter whose regulation is known and can be governed can be used for governing in a known manner the expression of any gene.
The filamentous fungus Ashbya gossypii is of biotechnological and economic interest. It is particularly interesting owing to its characteristic of being able to produce large amounts of riboflavin (see, for example, Kurth et al. (1996) Riboflavin, in: Ullmann""s Encyclopedia of Industrial Chemistry, VCH Weinheim). In addition, it is also interesting for the production of other metabolites and constituents. These constituents can be, for example, amino acids, vitamins, proteins, but also other substances of the primary and secondary metabolism, or other biopolymers.
The use of recombinant methods is promising for optimizing the production of such constituents in Ashbya gossypii and also in other organisms.
To carry out such an approach, genetic regulators (in particular promoters) of Ashbya gossypii itself are of great importance. Particularly interesting are those (so-called strong) promoters which make possible the overexpression of genes in Ashbya gossypii. Such strong promoters from Ashbya have not been described to date.
It is an object of the present invention to provide strong regulation elements for the transcription (promoters), which can principally be used in filamentous fungi, in particular those of the genus Ashbya.
A subject-matter of the invention is a DNA sequence which is suitable as promoter, containing
a) the primary structure shown in SEQ ID NO:1 position 9 to 307 or
b) a primary structure which hybridizes with the double strand containing a) under standard conditions and which has essentially the same promoter activities as a).
A promoter activity is termed essentially the same when the transcription of the A. gossypii GAP structural gene does not differ by more than 25%, preferably 10%, from a comparative value.
A particularly preferred promoter is the DNA sequence shown in SEQ ID NO:1 which at the 5xe2x80x2 and 3xe2x80x2 end has an NotI restriction cleavage site which is 8 nucleotides long in each case and which makes the promoter easily portable.
Important features for the function as promoter are:
the bona-fide TATA Box (nt 224-230), two sequence sections (nt 43-51 and 77-85) which correspond to the recognition sequence of the GCR1 binding element and
a sequence section (nt 9-20) whose complement partially corresponds to the recognition sequence of the RAPI binding element.
Subject-matter of the invention is also the use of the promoter sequences according to the invention in expression cassettes, where the promoter sequences are functionally linked to one or more structural genes. The term functional linkage describes such an arrangement of DNA sequences as to permit transcription of the structural gene(s).
Host organisms such as bacteria, yeasts, fungi, animals and plants can be transformed with the aid of such expression cassettes. Preferred host organisms are yeasts and fungi, in particular filamentous fungi like those of the genus Ashbya.
Subject-matter of the invention is also a method for the recombinant production of fine chemicals in host organisms, where a host organism is transformed with one of the expression cassettes described above, and this expression cassette contains one or more structural genes which encode the desired fine chemical or catalyze the biosynthesis of the desired fine chemical, the transformed host organism is cultured and the desired fine chemical is isolated from the culture medium.
This method is widely applicable to fine chemicals such as enzymes, vitamins, amino acids, sugars, fatty acids and natural and synthetic flavorings, aromas and colorants. The transformed host organisms are cultured and the fine chemical is isolated from the host organisms or the culture medium by methods known to the skilled worker.